Climate and Average Weather Year Round in Los Alamos United States

In Los Alamos, the summers are long, comfortable, arid, and clear and the winters are cold, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 38°F to 73°F and is rarely below 30°F or above 82°F.

Based on the tourism score, the best time of year to visit Los Alamos for warm-weather activities is from late June to mid September.

The warm season lasts for 4.0 months, from June 21 to October 22, with an average daily high temperature above 71°F. The hottest month of the year in Los Alamos is August, with an average high of 73°F and low of 55°F.

The cool season lasts for 3.4 months, from December 1 to March 14, with an average daily high temperature below 63°F. The coldest month of the year in Los Alamos is December, with an average low of 39°F and high of 61°F.

In Los Alamos, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in Los Alamos begins around May 4 and lasts for 5.9 months, ending around October 31.

The clearest month of the year in Los Alamos is August, during which on average the sky is clear, mostly clear, or partly cloudy 92% of the time.

The cloudier part of the year begins around October 31 and lasts for 6.1 months, ending around May 4.

The cloudiest month of the year in Los Alamos is February, during which on average the sky is overcast or mostly cloudy 44% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Los Alamos varies throughout the year.

The wetter season lasts 4.7 months, from November 13 to April 4, with a greater than 11% chance of a given day being a wet day. The month with the most wet days in Los Alamos is February, with an average of 6.0 days with at least 0.04 inches of precipitation.

The drier season lasts 7.3 months, from April 4 to November 13. The month with the fewest wet days in Los Alamos is August, with an average of 0.1 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Los Alamos is February, with an average of 5.9 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 22% on February 20.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Los Alamos experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 6.6 months, from October 12 to April 30, with a sliding 31-day rainfall of at least 0.5 inches. The month with the most rain in Los Alamos is February, with an average rainfall of 3.2 inches.

The rainless period of the year lasts for 5.5 months, from April 30 to October 12. The month with the least rain in Los Alamos is July, with an average rainfall of 0.0 inches.

The length of the day in Los Alamos varies significantly over the course of the year. In 2024, the shortest day is December 21, with 9 hours, 49 minutes of daylight; the longest day is June 20, with 14 hours, 29 minutes of daylight.

The earliest sunrise is at 5:47 AM on June 12, and the latest sunrise is 1 hour, 36 minutes later at 7:23 AM on November 2. The earliest sunset is at 4:49 PM on December 4, and the latest sunset is 3 hours, 29 minutes later at 8:18 PM on June 28.

Daylight saving time (DST) is observed in Los Alamos during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level in Los Alamos, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Los Alamos experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 4.6 months, from February 4 to June 24, with average wind speeds of more than 9.0 miles per hour. The windiest month of the year in Los Alamos is May, with an average hourly wind speed of 10.2 miles per hour.

The calmer time of year lasts for 7.3 months, from June 24 to February 4. The calmest month of the year in Los Alamos is August, with an average hourly wind speed of 7.7 miles per hour.

The predominant average hourly wind direction in Los Alamos varies throughout the year.

The wind is most often from the west for 3.0 months, from May 30 to August 30, with a peak percentage of 55% on July 19. The wind is most often from the north for 9.0 months, from August 30 to May 30, with a peak percentage of 44% on January 1.

Los Alamos is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.6 months, from July 21 to November 9, with an average temperature above 60°F. The month of the year in Los Alamos with the warmest water is September, with an average temperature of 61°F.

The time of year with cooler water lasts for 3.3 months, from February 24 to June 3, with an average temperature below 56°F. The month of the year in Los Alamos with the coolest water is April, with an average temperature of 55°F.

To characterize how pleasant the weather is in Los Alamos throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Los Alamos for general outdoor tourist activities is from late June to mid September, with a peak score in the first week of August.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Los Alamos for hot-weather activities is from early July to late September, with a peak score in the last week of August.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Los Alamos typically lasts for 9.2 months (279 days), from around February 26 to around December 1, rarely starting before January 3 or after April 7, and rarely ending before November 13 or after December 22.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms in Los Alamos should appear around January 29, only rarely appearing before January 21 or after February 11.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.9 months, from April 28 to August 23, with an average daily incident shortwave energy per square meter above 7.4 kWh. The brightest month of the year in Los Alamos is June, with an average of 8.5 kWh.

The darker period of the year lasts for 3.3 months, from November 5 to February 13, with an average daily incident shortwave energy per square meter below 3.9 kWh. The darkest month of the year in Los Alamos is December, with an average of 2.8 kWh.

For the purposes of this report, the geographical coordinates of Los Alamos are 34.744 deg latitude, -120.278 deg longitude, and 571 ft elevation.

The topography within 2 miles of Los Alamos contains very significant variations in elevation, with a maximum elevation change of 1,073 feet and an average elevation above sea level of 765 feet. Within 10 miles contains very significant variations in elevation (2,372 feet). Within 50 miles contains large variations in elevation (6,814 feet).

The area within 2 miles of Los Alamos is covered by grassland (78%) and cropland (16%), within 10 miles by grassland (70%) and shrubs (18%), and within 50 miles by water (43%) and shrubs (25%).